Lab Values

LAB VALUES OVERVIEW

Lab values can vary based on the source; therefore, it is essential to use the ranges found in your Medical-Surgical textbook for testing. Lab results are grouped as per testing categories, focusing on major tests and their components.

COMPLETE BLOOD COUNT (CBC)

The components of a Complete Blood Count (CBC) include Red Blood Cells (RBC), Hemoglobin (HGB), Hematocrit (HCT), Red cell distribution width (RDW), Blood indices, Platelet count, and White Blood Cells (WBC), along with differentials.

RED BLOOD CELLS (RBC)

RBCs have separate reporting standards for men and women, where normal values for men are 4.7 – 6.1 million/cu mm, and for women, it is 4.2 – 5.4 million/cu mm. Hemoglobin and Hematocrit provide better insights into the oxygen-carrying capacity than RBC count alone.

INCREASED RBC CAUSES

Several conditions can lead to an increase in RBC counts, including chronic lung disease, living at high altitudes, congenital heart defects (cyanosis), polycythemia (increased RBCs for unexplained reasons), and hemoconcentration due to low plasma volume (e.g., dehydration).

DECREASED RBC CAUSES

Conversely, decreased RBC counts can result from abnormal loss or destruction (hemorrhage), hormonal deficiencies affecting production, bone marrow suppression, or hemodilution, a perceived decrease due to higher plasma volume (e.g., during pregnancy).

HEMOGLOBIN (HGB)

Hemoglobin is the oxygen-carrying compound in RBCs, which gives blood its red color. Normal values for HGB are 14 – 18 g/100 ml for men and 12 – 16 g/100 ml for women. Decreased HGB levels are typically associated with conditions like anemia, hemorrhage, hemodilution, or nutritional deficits. Any condition that decreases RBCs will also lead to lower HGB and HCT levels. In contrast, increased HGB occurs under similar principles as those leading to increased RBC, excluding conditions like iron deficiency and pernicious anemia.

HEMATOCRIT (HCT)

Hematocrit measures the proportion of blood volume occupied by RBCs and is typically three times the HGB value. The normal range for men is 42 – 52%, while for women, it is 37 – 47%. HCT measurements are composed of plasma (water, proteins, nutrients, hormones), buffy coat (WBCs and platelets), and hematocrit (RBCs). Decreased HCT results from hemodilution, hemolysis, or a true decrease in RBCs, while increased HCT can occur due to polycythemia or hemoconcentration from dehydration.

ERYTHROCYTE (RBC) INDICES

Erythrocyte indices measure the quality and characteristics of RBCs, which are valuable in diagnosing different forms of anemias. Result alterations can be influenced by vitamin levels, such as B6, B12, and folic acid. Mean Corpuscular Volume (MCV) indicates average RBC size, being macrocytic (elevated) in vitamin deficiency and microcytic (decreased) in iron deficiency. Mean Corpuscular Hemoglobin (MCH) indicates the weight of hemoglobin in the average RBC, elevated in macrocytic anemia and decreased in microcytic. Mean Corpuscular Hemoglobin Concentration (MCHC) measures the saturation of hemoglobin in RBCs; it is elevated in conditions with high hemoglobin concentrations and decreased in low ones.

RED CELL DISTRIBUTION WIDTH (RDW)

RDW indicates the variability in RBC size, with a normal range of 11.5-14.5. An elevated RDW can indicate recent blood loss or failure to produce new RBCs.

WHITE BLOOD CELLS (WBC)

WBCs play a crucial role in fighting infections and coordinating inflammation responses. The normal adult range is 5-10 x 10^3, with critical values defined as < 2,500 or > 30,000. Elevated WBC counts can result from infections, malignancy, tissue necrosis, or inflammation (e.g., post-surgery), while decreased counts may be due to bone marrow suppression or supply exhaustion, leading to leukopenia, critically low WBC levels. Neutropenic precautions must be observed for patients with low WBC counts to prevent infections, including managing room cleanliness and dietary restrictions.

WBC DIFFERENTIAL

The WBC differential comprises various types of WBCs essential for determining overall function and responses to infections. Granular leukocytes include Neutrophils (55%-70%), Eosinophils (0.5%-1.5%), and Basophils (0.4%-1%). Nongranular leukocytes consist of Lymphocytes (20%-40%) and Monocytes (2%-8%). Neutrophils are critical in the body’s response to infections and inflammation, with high counts seen during infections. Eosinophils respond to allergic reactions and parasitic infections, while Basophils are associated with healing processes and sometimes seen in allergic responses. Lymphocytes play a significant role in specific immune responses, elevated in infections and cancers affecting the lymphatic system. Monocytes act as a second line of defense post-neutrophils, cleaning debris and combating chronic infections.

PLATELETS

The normal platelet range is 150,000 – 400,000 /μL. Critical platelet counts can indicate the potential for sepsis.

SEPSIS PROTOCOL

Upon suspicion of severe infection, a sepsis protocol should be initiated, including cultures, a lactic acid check, and intravenous fluids.

CARDIAC ENZYMES

Cardiac enzymes such as Creatine Kinase (CK) rise during myocardial infarction and peak at day one; they help distinguish between skeletal and cardiac damage. Troponin serves as a sensitive biomarker for myocardial damage, with significant elevation indicating a heart attack.

D-DIMER AND C-REACTIVE PROTEIN (CRP)

D-Dimer indicates clot breakdown, with elevation seen in conditions like Deep Vein Thrombosis (DVT); CRP signals inflammation and tissue injury, with increased levels potentially indicating elevated cardiovascular risk.

BNP (BRAIN NATRIURETIC PEPTIDE)

BNP is secreted during heart failure, with low levels indicating normal function.